I recently cleaned up an old shotgun for a friend. It is a 12 bole single shot gun.  It has a heavy butplate similar to military muskets.
 
I have a couple of bits of these which suggest that there were at least three in the immediate locality.
 
They appear to be made by Cutting off the back end of a musket and threading the bottom to attach it onto the mauser bolt action.
 
I there a history to these firearms - for instance were they originaly police (RIC) weapons.
 
It is possibble that the musket stock was also adapted to take the new action - hence the serious butt plate.
 
any ideas
 
david